/*
 * EAP-PEAP common routines
 * Copyright (c) 2008, Jouni Malinen <j@w1.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 */

#include "includes.h"

#include "common.h"
#include "sha1.h"
#include "eap_peap_common.h"

void peap_prfplus(int version, const u8 *key, size_t key_len,
                  const char *label, const u8 *seed, size_t seed_len,
                  u8 *buf, size_t buf_len)
{
        unsigned char counter = 0;
        size_t pos, plen;
        u8 hash[SHA1_MAC_LEN];
        size_t label_len = os_strlen(label);
        u8 extra[2];
        const unsigned char *addr[5];
        size_t len[5];

        addr[0] = hash;
        len[0] = 0;
        addr[1] = (unsigned char *) label;
        len[1] = label_len;
        addr[2] = seed;
        len[2] = seed_len;

        if (version == 0) {
                /*
                 * PRF+(K, S, LEN) = T1 | T2 | ... | Tn
                 * T1 = HMAC-SHA1(K, S | 0x01 | 0x00 | 0x00)
                 * T2 = HMAC-SHA1(K, T1 | S | 0x02 | 0x00 | 0x00)
                 * ...
                 * Tn = HMAC-SHA1(K, Tn-1 | S | n | 0x00 | 0x00)
                 */

                extra[0] = 0;
                extra[1] = 0;

                addr[3] = &counter;
                len[3] = 1;
                addr[4] = extra;
                len[4] = 2;
        } else {
                /*
                 * PRF (K,S,LEN) = T1 | T2 | T3 | T4 | ... where:
                 * T1 = HMAC-SHA1(K, S | LEN | 0x01)
                 * T2 = HMAC-SHA1 (K, T1 | S | LEN | 0x02)
                 * T3 = HMAC-SHA1 (K, T2 | S | LEN | 0x03)
                 * T4 = HMAC-SHA1 (K, T3 | S | LEN | 0x04)
                 *   ...
                 */

                extra[0] = buf_len & 0xff;

                addr[3] = extra;
                len[3] = 1;
                addr[4] = &counter;
                len[4] = 1;
        }

        pos = 0;
        while (pos < buf_len) {
                counter++;
                plen = buf_len - pos;
                hmac_sha1_vector(key, key_len, 5, addr, len, hash);
                if (plen >= SHA1_MAC_LEN) {
                        os_memcpy(&buf[pos], hash, SHA1_MAC_LEN);
                        pos += SHA1_MAC_LEN;
                } else {
                        os_memcpy(&buf[pos], hash, plen);
                        break;
                }
                len[0] = SHA1_MAC_LEN;
        }
}
